Designing a MEMS sensor to operate in a harsh environment presents a number of issues. An example is a MEMS pressure sensor incorporated in a rechargeable lithium ion battery system. In order to guarantee reliable operation the parts that may be in direct contact with the liquid electrolyte inside the cell should effectively block water and Li-ion diffusion and other heavy metal ions typically present in such cells (Mn2+, Co2+, Fe2+/3+). Especially the pressure membrane that may be in direct contact with the liquid electrolyte may be subject to potential water and Li-ion penetration because it may be flexible and thin. If diffusion occurs in the pressure membrane, pressure sensor operation may critically degrade. Accordingly, designing an accurate MEMS sensor requiring a membrane in a harsh environment where it is necessary to provide an effective barrier against various materials present in the operating environment presents a number of issues.